Make FileUtil::CreateDirectory idempotent.

* If the directory already exists, returns OkStatus and does nothing.
* Will suppress the warning in the beginning of logging.
* Will fix #900

PiperOrigin-RevId: 629129254

src/base/file_util.cc

@@ -198,6 +198,10 @@ absl::Status FileUtil::CreateDirectory(const std::string &path) {
 }
 
 absl::Status FileUtilImpl::CreateDirectory(const std::string &path) const {
+  // If the path already exists, returns OkStatus and does nothing.
+  if (const absl::Status status = DirectoryExists(path); status.ok()) {
+    return absl::OkStatus();
+  }
 #if defined(_WIN32)
   const std::wstring wide = win32::Utf8ToWide(path);
   if (wide.empty()) {

src/base/file_util.h

@@ -92,6 +92,7 @@ class FileUtil {
   ~FileUtil() = delete;
 
   // Creates a directory. Does not create directories in the way to the path.
+  // If the directory already exists, returns OkStatus and does nothing.
   static absl::Status CreateDirectory(const std::string &path);
 
   // Removes an empty directory.

src/base/file_util_test.cc

@@ -74,6 +74,9 @@ TEST(FileUtilTest, CreateDirectory) {
   EXPECT_OK(FileUtil::CreateDirectory(dirpath));
   EXPECT_OK(FileUtil::DirectoryExists(dirpath));
 
+  // Create the same directory again.
+  EXPECT_OK(FileUtil::CreateDirectory(dirpath));
+
   // Delete the directory.
   ASSERT_OK(FileUtil::RemoveDirectory(dirpath));
   ASSERT_FALSE(FileUtil::FileExists(dirpath).ok());